Engine starter drive



0612. 13, 1953 J, DIGBY 2,655,048

ENGINE STARTER DRIVE Filed Aug. 11, 1952 z6 2 %z5 6638 Z 1? w Z9 31 3a 5 I; A 15 g? 11 vfi 1 1? 9 959 i #3412151 78 .35 36 35 I 6 P I INVEIY TOR.

A TTORNE Y Patented Oct. 13, 1953 ENGINE STARTER DRIVE James J. Digby, Elmira, N. Y., assignor to Bendix.

Aviation Corporation, a corporation of Delaware Application August 11, 1952, Serial No. 303,734

4 Claims.

The present invention relates to an engine starter drive and more particularly to that form of automatically engaging type of gearing which is arranged to maintain the connection between the starting motor and engine to be started until the engine is reliably self-operative.

It is an object of the present invention to provide a novel engine starter drive which is simple in construction, economical to manufacture and efiicient in operation.

It is another object to provide such a device which incorporates means for ensuring that the engagement of the drive takes place with a minimum of shock and wear of the parts.

It is another object to provide such a device including a centrifugal detent-latch member for positively holding the drive pinion in engagement with the'engine gear until the engine is started, and for preventing the drive pinion from drifting away from its idle position when the engine is running;

It is another object to provide such a device in which the centrifugal member rotates at the speed of the starting motor during the engaging movement of the pinion, and at the speed of the pinion during the disengaging movement of the pinion.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation, partly broken away and in section of a starter drive forming a pie ferred embodiment of the invention showing the parts in idle position;

Fig. 2 is a similar view showing the parts in cranking position;

Fig. 3 is a similar view showing the parts in their positions when the engine has started and the pinion is overrunning the starting motor while remaining in mesh with the engine gear; and

Fig. 4 is a similar view showing the parts in the positions assumed in case of tooth abutment between the pinion and engine gear during the meshing movement of the pinion.

In Fig. l. of the drawing there is illustrated a power shaft I which may be the extended armature shaft of a starting motor not illustrated. A driving head 2 is fixedly mounted on the free end of the power shaft as by means of a cross pin 3, and has a flange 4 rigidly mounted thereon or formed integrally therewith.

A hollow screw shaft 5 is slidably journaled on the power shaft adjacent the drive head and is provided with-projecting tongues B which are received in corresponding slots I in the hub 8- of a pinion 9 which is also slidably journaled onthe power shaft for longitudinal movement into and out of mesh with a gear II of the engine to be started. A driving clutch member I2 is slidably and rotatably mounted on the screw shaft 5; and is provided with overrunning clutch teeth I3 adapted to cooperate with similar teeth I4 on a driven clutch member I 5 which is in the form of a nut threaded on the screw shaft. A barrel member I6 which surrounds and encloses the clutch members I2, I5 is rigidly mounted at one end as indicated at I! on the flange 4 of the driving head 2, and at the other end has an inturned flange I3 embracing the clutch nut member I5; A spring member I9 located between the flange I8 of the barrel and a shoulder 2I on said nut serves to yieldingly hold the overrunning clutch teeth in engagement.

The driving clutch member I2 has radial projections 22 formed thereon which slidably engage in slots 23' in the barrel so as to form a splined connection between the barrel and driving clutch member, and a cylindrical block 24 of rubber or other elastically deformable material, is located in the barrel I6, seated at one end on the driving clutch member I2, and at its other end bearing against a thrust washer 25 which is in contact with the flange 4 of the driving head 2. The ends 26 of the slots 23 are so positioned as to maintain the yielding member 24 under a predetermined initial compression.

Means for limiting the relative longitudinal movement of the screw shaft and pinion is provided in the form of a split thrust ring 21 which is seated in registering grooves 28, 29 (Fig. 2) in the tongues 5 of the screw shaft and the hub 8 of the pinion, the width of the grooves 29 being sufficient to permit the desired amount of relative longitudinal movement between the pinion and screw shaft.

An annular weight member 3I is splined on the hub 8 of the pinion 9 and is yieldably urged against the lock ring 21 by means of a spring 32 located in a counterbore of the weight member and, bearing against shoulders 33 on the pinion. The spring 32 thus serves to urge the weight member 3| away from the toothed portion of the pinion, and also serves to yieldably maintain the pinion in extended relation to the screw shaft as shown in Fig. 1.

The screw shaft 5 is formed with an inclined shoulder 34 and with a stop shoulder 35. A detent-latch member 36 is mounted in the nut I5 for radial sliding movement and is pressed against the screw shaft by a spring member 31 which is confined in the nut l5 by. a cup member 38 having a press fit in the nut. 'The detentlatch member 36 is positioned to engage the inclined shoulder 34 on the screw shaft when the parts are in idle position as shown in Fig. 1 to prevent drifting of the parts toward meshing position while the engine is running; and also cooperates with the shoulder 35 on the screw shaft to prevent demeshing movement of the parts after the engine is cranked, until the rotation of the parts is sufficiently rapid to withdraw the member 36 by centrifugal force.

In the operation of the device, starting with the parts in the positions illustrated in Fig. 1, energization of the starting motor causes rotation of the power shaft l in the direction of the arrow 0. which is transmitted through the driving head 2, barrel i6, and clutch member l2 to the clutch nut E5. The screw shaft 5 is thereby traversed to the right, propelling the pinion with it, until the pinion meshes with the engine gear II, at which time the pinion engages a thrust bearing 39 fixed on the power shaft. During the meshing movement of the parts, resistance of the centrifugal detent 36 to such movement is reduced by the effect of centrifugal force since the nut member 15 is in rotation with clutch member [2. When the meshing movement of the pinion 9 is arrested by the thrust bearing 39, the screw shaft continues its forward movement until it engages against the end of the pinion hub B as shown at Al in Fig. 2. Thereupon the nut I5 is traversed backward, compressing the yielding member 24 and forcing the overrunning clutch teeth l3, l4 tightly together until sufficient torque is built up to rotate the engine gear ll.

When the engine starts, the acceleration of pinion 9 is transmitted to the screw shaft 5 causing the pinion and screw shaft to move back until the shoulder 35 of the screw shaft engages the centrifugal latch 36 and arrests this demeshing movement, whereupon the nut i5 overruns the driving clutch member I2 as shown in Fig. 3. When the rotary speed of the overrunning parts is sufficient to withdraw the centrifugal member 36 from the shoulder 35, the parts are returned to idle position where they are yieldingly maintained by the engagement of the member 36 against the inclined shoulder 34 of the screw shaft.

If, during the meshing movement, a tooth of the pinion should abut against a tooth of the engine gear II as shown in Fig. 4, the meshing movement of the pinion is momentarily arrested, while the spring 32 is compressed. During the time interval so provided, the torque transmitted through the screw shaft indexes the pinion teeth into proper registration with the tooth spaces of the engine gear and meshing proceeds by the expansion of the spring 32 and resumption of the travel of the parts. It will be noted that since the weight member 3| is splined on the pinion, the longitudinal movement of the weight member 3| is not arrested during the mesh-enforcing action. Since the inertia of the pinion by itself is quite small, it will be appreciated that the shock and wear caused by the mesh-enforcing action is reduced to a minimum.

Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an engine starter drive a power shaft, a driving head fixed thereon, a driving overrunning clutch member yieldably connected to rotate with the driving head, a screw shaft slidably journaled on the power shaft, a driven clutch member threaded on the screw shaft, yielding means normally holding the clutch members in engagement, a pinion slidably journaled on the power shaft and slidably but non-rotatably connected to the screw shaft, means for limiting relative longitudinal movement of the pinion and screw shaft, yielding means for holding the pinion in extended relation with respect to the screw shaft, and an abutment on the power shaft defining the operative position of the pinion.

2. An engine starter drive as set forth in claim 1 including further a centrifugal detent mounted in the driven clutch member, said screw shaft having a shoulder cooperating with the detent to resist longitudinal movement of said clutch member on the screw shaft.

3. An engine starter drive as set forth in claim 1 including further an annular weight member slidably but non-rotatably mounted on the pinion, means limiting movement of the weight member thereon in the direction away from the operative position of the pinion, said yielding means for holding the pinion extended serving also to urge the weight member against said abutment.

4. An engine starter drive as set forth in claim 3 in which the means for limiting relative longitudinal movement of the pinion and screw shaft also provides the means for limiting the longitudinal movement of the weight member on the pinion.

JAMES J. DIGBY.

No references cited. 

